Isotope separating apparatus



Jilly 26, 1955 13, 2,714,165

ISOTOPE SEPARATING APPARATUS Filed June 28, 1946 INVENTOR. John D. Reid.

Wm: BY

Q W4 W United States Patent rsororn SEPARATING APPARATUS John D. Reid, Oak Ridge, Tenn, assignor, by mesne assignments, to the United States of America as represented by the United States Atomic Energy Commission Application June 28, 1946, Serial No. 679,882

Claims. (Cl. 25041.9)

This invention relates generally to electromagnetic isotope separating apparatus of the type commonly referred to as a calutron, and is more particularly concerned with that portion of such apparatus, herein referred to as the ion beam transmitter, which includes the ion source for generating a supply of positive ions of the material the isotopes of which it is desired to separate, together with its associated accelerating electrode system for withdrawing these ions from the source and projecting them in the form of a high velocity beam into the interior region of the calutron where the separation is effected.

In a calutron, it is necessary that the ion beam transmitter be supported in a cantilever. fashion from a vertical face plate which forms the front end of the calutron. Since the position of the transmitter and its parts within the calutron is extremely critical, and since the transmitter itself is a heavy cumbersome piece of equipment, the manner of support is a major problem in the design of such equipment. This problem is further complicated by the requirement that various portions of the transmitter be insulated from each other and from the supporting face plate. Furthermore, all insulating and supporting elements are subject to the deteriorative conditions which exist within an operating calutron and which arise whenever a highly evacuated region containing charged particles is subjected simultaneously to crossed electric and magnetic field of high intensity; in other words, these elements, during calutron operation, are being continuously bombarded by charged particles which results in troublesome crudding, erosion and heating.

In the past, the primary support for the main portion of the transmitter was provided by a bushing or tube of insulating material extending horizontally from the face plate and having the transmitter mounted on the end thereof. This supporting bushing, however, often failed during operation and required frequent replacement, and the arrangement was never considered entirely satisfactory.

The present inventor has conceived that a primary factor contributing to the unsatisfactory performance of the prior arrangement for supporting and insulating the transmitter, was the peculiar combination of stresses to which the supporting bushing was subjected, that is, besides the stress set up in the insulating material from the intense electric field, the bushing was also under the tensile stress of a cantilever beam. It is known, of course, that insulating material is rotably weak in tension. The present inventor, therefore evolved supporting and insulating arrangement wherein these particular two types of stresses do not occur in any one element.

According to the present arrangement, the primary support for the transmitter is derived from a metallic tube or cylinder extending horizontally from the face plate and being provided on its end with a vertically extending block of insulating material which in turn supplies the support for the ion source. It will be apparent that in this case only the metallic tube is subject to tension. The insulat- "ice ing block, besides the electrical stress, is subject only to compression, which it is, of course, much better able to withstand than tension. Two additional insulating bushings extend through the face plate for the purpose of bringing into the equipment the required high voltage leads, but these bushings are not required to provide any mechanical support. A suitable water cooling system is provided to keep the temperature of operating parts of the transmitter down to a reasonable value.

Accordingly, the primary object of the invention is to provide a satisfactory arrangement for suitably supporting and insulating the various component portions of an ion beam transmitter within a calutron.

Another object of the invention is to provide an improved design of a calutron ion beam transmitter and the associated calutron structure.

Other objects and advantages of the invention will become apparent from the following description, taken in connection with the accompanying drawings, wherein one embodiment of the invention is illustrated.

In the drawings,

Fig. 1 is a diagrammatic perspective view of the type of isotope separating apparatus or calutron to which the present invention has particular reference.

Fig. 2 is a diagrammatic perspective view of a calutron ion beam transmitter and its associated calutron parts constructed and arranged according to the principles of the present invention.

Fig. 3 is a front view of the supporting face plate showing the voltage relationship of the various lead-in conductors.

Referring to Fig. 1 of the drawings, there is shown schematically the way in which an isotope separating apparatus may be set up, and in connection with which, an

' ion beam transmitter may be utilized which very ad vantageously makes use of the principles of my invention. In Fig. 1, numeral 10 designates a rectilinear evacuated tank in which the process is carried out. The tank has an outlet 11 at the back which may be connected to a suitable evacuating system, not shown, consisting ordinarily of a diffusion pump backed up by a rotary mechanical pump. On opposite sides of tank 10 are laminated iron cores or pole pieces, as designated at 16, and wound around these pole pieces are electrical windings 17. The cores and windings produce an intense magnetic field which is in a direction perpendicular, that is, traverse with respect to the tank.

Within the tank 10 is a liner structure 18 having the general shape and configuration as shown in Fig. l, and the interior of the liner is evacuated as well as the remainder of the interior of the tank. The tank 10 has a relatively large main vertical face plate 20 at the front which is attached to the tank in a manner to form a seal between the tank and the face plate, and it supports the liner structure 18 within the tank. Numerals 21 and 22 designate lower and upper sub-face plates, respectively, attachable to the main face plate 20 in a sealing manner, and cooperating respectively with the lower and upper portions of the liner structure 18. The lower face plate 21 carries or supports the ion beam transmitter, as will later be described in detail, and the upper face plate 22 supports the receiving structure, the transmitter being operable to project a beam of ions into the liner 18 which beam is bent into the arc of a circle under the influence of the magnetic field, whereby the separated components of the beam may be separately collected by the receiving structure carried by face plate 22.

Referring now to Figs. 2 and 3, the lower sub-face plate 21, hereinafter referred to as the face plate, is shown with the ion beam transmitter structure attached thereto. Reference numeral 25 designates a hollow cylinder or tube, which may preferably be formed of stainless steel,

and which supports on its ends the various portions of the ion beam transmitter. The tube thus operates as a cantilever beam having tensile stresses set up therein. Tube 25 is'in turn supported from. the face plate 21 to which it. is attached in a vacuum sealing relationship.

Themajor portion of the'weight ofthe ion beam transmitter resides in the ion source portion thereof, which portion is indicated generally at 24. The ion source unit 24 is supported by a column or block 23, which is made of insulating material and is attached to the tube 25, as shown, so as to operate as a compression supporting column. V The ion source unit 24 involves a rectilinear chamber or housing 26 which sets directly upon the insulator block 23. Within housing 26 is a container, not shown, which contains acharge of the solid material to be ionized, and has associated with it heating means, not shown, for vaporizing the charge material. The vapor of the charge material is then constrained'to flow by means of suitable baffles and passageways into two constricted and elongated ionization chambers, which chambers are contiguous with elongated ion beam exit slots 32 and 32, respectively, but which, of course, are interiorly disposed within the chamber 26. These two ionization chambers form regions wherein the vapor is disassociated and deionized by an electric discharge maintained therein, as will later be fully explained. The details of construction of the above described interiorly located portions of ion source may be as described in detail in U. S. application Serial No. 609,661 for Electron Control Apparatus, filed August 8, 1945, in the name of Howard W. Savage.

The apparatus for forming the ionizing electric discharge or arcs within the ionization chambers embodies the utilization of secondary electron emission phenomenon, and this apparatus is constructed in accordance with the principles disclosed in U. S. application Serial No. 649,404 entitled, Electron Emitter, and filed February 21, 1946 in the name of the present inventor. As therein disclosed, and referring to the lower of the two identical sets of ionization arc apparatus, an ordinary thermionic filament 27 is electrically heated so as to provide bombarding electrons for the secondary electron emitter 28, which is disposed behind and aligned with a collimating slot 29 formed in a collimating plate 30. Secondary electron emitter 28 can not be seen in the drawings, but its position and construction can be seen from the corresponding emitter 28' for the upper ionization arc apparatus associated with ion beam exit slot 32'. As will later be explained in detail emitter 28 is maintained at a very high positive potential with respect to the filament 27 and collimating plate 30, both of which are at the same potential. Accordingly, emitter 28 is bombarded with high energy electrons from filament 2,7, and emitter 28 in turn emits secondary electrons.

A slot 31 is formed in housing 26 at one end of the lower ionization chamber. Emitter 28 is maintained at a negative potential of perhaps a few hundred volts with respect to housing 26 so that it forms a cathode having the housing 26 as its anode. Thus, an electric ionization arc is struck between the emitter 28 and housing 26 and this arc, being constrained to flow in the direction of the magnetic field H, extends through slot 31 and lengthwise along the interior of the ionization chamber thereby disassociating and ionizing the charge vapor contained there- Considering now the manner of support and insulation of the various portions of the ionization arc apparatus, and referring also to Fig. 3 in order to clarify the voltage relationship of the various portions, face plate 21 and the metallic tube 25 are ordinarily grounded as shown, although the ground may, of course, be placed at any point in the potential system. The polarities of the various voltages are from minus to plus in the direction of the arrows in Fig. 3. The ion source 24, that is, the housing 26 and the portions contained therein, are maintained at a high positive potential V1 of perhaps 35 kv. by means of lead 33 which is brought into the interior of the tank through an insulated sealing bushing 34. The emitter 28 is maintained at a negative potential V3 of perhaps a few hundred volts with respect to housing 26 by means of lead 35 which is also brought through bushing 34, and which connects to the support 36 for emitter 28. Support 36 is of conducting material and is suitably attached to but insulated from housing '26.

The remaining portion of the ionization arc apparatus is supported from a hollow upright 42 having a horizontally extending portion 43 at its bottom which attaches to tube 25. Upright 42 carries a pair of insulating blocks which engage the opposite terminals of filament 27. Leads 43 and 44, which may be in the form of water tubes for cooling purposes, connect to the opposite terminals of filament 27 so as to apply the fila ment supply voltage V4 to the filament. One side of the filament supply voltage Vt may be grounded, as shown in Fig. 3, so that filament 27 is at substantially the same potential as upright 42, tube 25 and face plate 21. Leads 43 and 44 are brought through face plate 21 in a suitably sealing manner, and lead 43 must be slightly insulated from face plate 21.

Also attached to upright 42 is a supporting member 45 which carries the collimating plates 30 and 30 at its lower and upper extremities, respectively. Since the housing 26 is at a very large positive potential V1 with respect to filament 27 and at a comparatively low positive potential V3 with respect to emitter 23, the emitter 28 is also at a very high positive potential with respect to filament 27, and this high positive potential serves to accelerate bombarding electrons from the filament 27 to emitter 28.

It will be understood that the upper ionization arc apparatus is identical with the lower ionization arc apparatus described above. Upright 42 and supporting member 45, which respectively carry filaments 27, 27 and collimating plates 30, 30' are broken away so that portions of the lower ionization arc apparatus which are not visible in the drawing may be seen in the upper ionization arc apparatus. Separate filament supply voltages V4 for filaments 27 and 27' may be provided, if desired.

The accelerating system for withdrawing the positive ions formed in the upper and lower ionization chambers comprise electrodes 46 and 62 both of which have formed therein lower and upper elongated slots 47, 47' and 63, 63 to permit the passage of the ion beams formed thereby. Electrode 46 is maintained at a high negative potential V2 of perhaps 15 kv. with respect to ground by means of lead 66 which is brought into the tank through a second insulated sealing bushing 67, so that a potential difference of perhaps 50 kv. exists between this electrode andthe housing 26 for the purpose of accelerating the electrons outwardly. Electrode 46 is supported by vertical rods, onlythe left most one of which, designated 59, may be seen. These two rods are made of ceramic or insulating material and are in turn attached to the extremities of a horizontal cross bar 64 extending on both sides from tube 25. Electrode 62 is attached to the end of tube 25 in non-insulated relation by means of conducting upright 65, so that this electrode is at ground potential.

Covering three sides of the housing 26, that is, the top, the bottom and the back side nearest the face plate 21, is a shield having many small openings therein, as shown, to facilitate evacuation from between the shield and the housing. This shield 55 is supported from, and maintained at the same ground potential as, tube 25 by a bracket, not shown, and it has a'large opening in its back side to accommodate bushing 34 and a similar opening in its bottom part to accommodate insulator block 23.

Housing 26 has upstanding fins or ribs, as shown at 69, and these ribs may have a -V or chevron configuration looking down from above. Opposite legs of the configuration of ribs 60 are disposed at an angle to the direction of the magnetic field, that is, they are not perpendicular to the field nor are they parallel to the field. The top part of the shield 55 has downwardly extending battle members 61 which are interleaved between the associated fins 6t). The purpose of the shield 55 and particularly the fins 60 and bafiie members 61 are to inhibit electron oscillations and generally to protect portions of the ion source unit 24 from deterioration due to crudding and erosion during calutron operation, their operation in this respect being more completely explained in the aforementioned Howard W. Savage patent application.

A water cooling system is employed in the present apparatus for the purpose of maintaining the tube 25 and upright 42 at reasonable temperatures. Although the cooling system employed might take many dirierent and complex forms, a comparatively simple system is illustrated in the drawings. As shown, hollow tube 25 has coaxially disposed within it a smaller hollow tube or pipe 68. A pump, schematically'indicated at 69, connects to tube 25 and pipe 68 outside the tank so as to maintain a hydraulic pressure gradient between the cooling water within the pipe and tube, respectively. Pipe 68 is open at its end so as to allow cooling water to circulate in through pipe 68 and out again in the space between pipe .68 and tube 25.

Hollow upright 42 is indicated to be cooled in a similar manner, having within it a smaller pipe 70 which is connected to pipe 68. Pipe 70 will be understood also to be open at its upper end so as to allow cooling water to circulate from pipe 68 through pipe 70 and back again between the outsides of these pipes and the insides of upright 42 and tube 25.

Whilefor the purpose of illustrating the principles of the invention, a particular embodiment thereof has been specifically described, it is to be understood that the invention is not limited to the particular apparatus described, but is of the scope of the appended claims.

What is claimed is:

1. In isotope separating apparatus, in combination, an evacuated tank, a face plate adapted to seal an opening in said tank, a source of ions within said tank, a horizontal metallic supporting member extending inwardly from said plate and supporting said ion source in cantilever beam fashion, and a compression block of insulating material interposed between said ion source and said supporting member.

2. Apparatus, as claimed in claim 1, wherein said supporting member is formed of stainless steel.

3. Apparatus, as claimed in claim 1, wherein said supporting member is made hollow and contains a circulating cooling fluid.

4. In isotope separating apparatus, in combination, an evacuated tank, a face plate adapted to seal an opening in said tank, a source of ions within said tank, a horizontal metallic supporting member extending inwardly from said plate and supporting said ion source in cantilever beam fashion, a compression block of insulating material interposed between said ion source and said supporting member, an accelerating electrode structure associated with said ion source, and means for insulatedly supporting said structure from said supporting member.

5. In isotope separating apparatus, in combination, an evacuated tank, a face plate adapted to seal an opening in said tank, a source of ions within said tank, a horizontal metallic supporting member extending inwardly from said plate and supporting said ion source in cantilever beam fashion, a compression block of insulating material interposed between said ion source and said supporting member, an accelerating electrode structure associated with said ion source, and means for insulatedly supporting said structure from said supporting member, a decelerating electrode structure associated with said accelerating electrode structure, and means for supporting said decelerating electrode structure in conductive relationship from said supporting member.

6. In isotope separating apparatus, in combination, an evacuated tank, a face plate adapted to seal an opening in said tank, a source of ions within said tank, a horizontal metallic supporting member extending inwardly from said plate and supporting said ion source in cantilever beam fashion, a compression block of insulating material interposed between said ion source and said supporting member, an accelerating electrode structure associated with said ion source, means for insulatedly supporting said structure from said supporting member, a decelerating electrode structure associated with said accelerating electrode structure, means for supporting said decelerating electrode structure in conductive relationship from said supporting member, and means including sealing bushings extending through said plate and containing electrical leads for maintaining said ion source at a positive potential with respect to said supporting member and for maintaining said accelerating electrode structure at a negative potential with respect to said supporting member.

7. In isotope separating apparatus, in combination, an evacuated tank, a face plate adapted to seal an opening in said tank, a source of ions within said tank, a horizontal metallic supporting member extending inwardly from said plate and supporting said ion source in cantilever beam fashion, a compression block of insulating material interposed between said ion source and said supporting member, an accelerating electrode structure associated with said ion source, means for insulatedly supporting said structure from said supporting member, a decelerating electrode structure associated with said accelerating electrode structure, means for supporting said decelerating electrode structure in conductive relationship from said supporting member, means including sealing bushings extending through said plate and containing electrical leads for maintaining said ion source at a positive potential with respect to said supporting member and for maintaining said accelerating electrode at a negative potential with respect to said supporting member, a filamentary cathode associated with the ionizing portion of said ion source, and means including an upright attached to said supporting member for carrying said cathode.

8. Apparatus, as claimed in claim 7, wherein said supporting member and said upright are made hollow and contain a circulating cooling fluid.

9. In isotope separating apparatus, in combination, an evacuated tank, a face plate adapted to seal an opening in said tank, a source of ions within said tank, a horizontal supporting member extending inwardly from said plate and supporting said ion source in cantilever beam fashion, a compression block of insulating material interposed between said ion source and said supporting member, a filamentary cathode associated with the ionizing portion of said ion source, and means including an upright attached to said supporting member for carrying said cathode, said supporting member and said upright being interiorly channelled to accommodate the flow of a cooling fluid.

10. In isotope separating apparatus, in combination, an evacuated tank, a face plate adapted to seal an opening in said tank, a source of ions within said tank, a horizontal hollow supporting member extending inwardly from said plate and supporting said ion source in cantilever beam fashion, a compression block of insulating material interposed between said ion source and said supporting member, a filamentary cathode associated with the ionizing portion of said ion source, means including ahollow upright attached to said supporting member for carrying said cathode, and means for circulating a cooling fluid within said supporting member and said upright.

No references cited. 

1. IN ISOTOPE SEPARATING APPARATUS, IN COMBINATION, AN EVACUATED TANK, A FACE PLATE ADAPTED TO SEAL AN OPENING IN SAID TANK, A SOURCE OF IONS WITHIN SAID TANK, A HORIZONTAL METALLIC SUPPORTING MEMBER EXTENDING INWARDLY FROM SAID PLATE AND SUPPORTING SAID ION SOURCE IN CANTILEVER BEAM FASHION, AND A COMPRESSION BLOCK OF INSULATING MATERIAL INTERPOSED BETWEEN SAID ION SOURCE AND SAID SUPPORTING MEMBER. 